System and process for preparing polylactic acid nonwoven fabrics

ABSTRACT

A system for preparing a polylactic acid (PLA) spunbond nonwoven fabric is provided. In particular, the system includes a first PLA source configured to provide a stream of molten or semi-molten PLA resin; a spin beam in fluid communication with the first PLA source, the spin beam configured to extrude and draw a plurality of PLA continuous filaments; a collection surface disposed below an outlet of the spin beam onto which the PLA continuous filaments are deposited to form the PLA spunbond nonwoven fabric; a first ionization source positioned and arranged to expose the PLA continuous filaments to ions; and a calender positioned downstream of the first ionization source.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 15/666,675 filed Aug. 2, 2017, which claims the benefit ofpriority to U.S. Application No. 62/370,087 filed on Aug. 2, 2016, thecontents of which are both incorporated herein by reference in theirentirety for all purposes.

FIELD

The presently-disclosed invention relates generally to systems andprocesses for preparing nonwoven fabrics, and more particularly tosystems and processes for preparing polylactic acid (PLA) spunbondnonwoven fabrics.

BACKGROUND

Nonwoven fabrics are used in a variety of applications such as garments,disposable medical products, diapers, personal hygiene products, amongothers. New products being developed for these applications havedemanding performance requirements, including comfort, conformability tothe body, freedom of body movement, good softness and drape, adequatetensile strength and durability, and resistance to surface abrasion,pilling or fuzzing. Accordingly, the nonwoven fabrics which are used inthese types of products must be engineered to meet these performancerequirements.

Traditionally, such nonwoven fabrics are prepared from thermoplasticpolymers, such as polyester, polystyrene, polyethylene, andpolypropylene. These polymers are generally very stable and can remainin the environment for a long time. Recently, however, there has been atrend to develop articles and products that are consideredenvironmentally friendly and sustainable. As part of this trend, therehas been a desire to produce ecologically friendly products comprised ofincreased sustainable content in order to reduce the content ofpetroleum based materials.

Polylactic acid or polylactide-based polymers (PLA) provide acost-effective path to sustainable content spunbond nonwovens that canbe readily converted into consumer products. To fully capture thecost-effective benefits of PLA-based consumer products, PLA must beconvertible into nonwovens and then into the final consumer product atvery high speeds with minimal waste. However, it is difficult to combinethe steps of spinning, web formation, and bonding at the very highspeeds needed for the economically attractive production of spunbond PLAwith desired fabric properties.

To address this need, nonwovens have been developed having a sheath/corebicomponent structure in which the PLA is present in the core, and asynthetic polymer, such as polypropylene, is in the sheath. Suchnonwovens are described in U.S. Pat. No. 6,506,873. The presence of thesynthetic polymer in the sheath provides the necessary properties forcommercial production of nonwovens comprising PLA at high speeds.

Accordingly, there still exists a need for systems and processes forstatic protection during the processing of PLA.

BRIEF SUMMARY

One or more embodiments of the invention may address one or more of theaforementioned problems. Certain embodiments according to the inventionprovide systems and processes for preparing polylactic acid (PLA)spunbond nonwoven fabrics at high speeds. In particular, embodiments ofthe invention are directed to systems and processes that utilize meansfor controlling static, including ionization bars, to prepare PLAspunbond nonwoven fabric. In this regard, PLA processing can occur athigh speeds with minimal waste, thereby making spunbond PLA productioneconomically attractive.

In accordance with certain embodiments, the system includes a first PLAsource configured to provide a stream of molten or semi-molten PLAresin, a spin beam in fluid communication with the first PLA source, acollection surface disposed below an outlet of the spin beam onto whichthe PLA continuous filaments are deposited to form the PLA spunbondnonwoven fabric, a first ionization source positioned and arranged toexpose the PLA continuous filaments to ions, and a calender positioneddownstream of the first ionization source. The spin beam, according tocertain embodiments, is configured to extrude and draw a plurality ofPLA continuous filaments.

In another aspect, certain embodiments according to the inventionprovide a process for preparing a polylactic acid (PLA) spunbondnonwoven fabric. In accordance with certain embodiments, the processincludes providing a stream of molten or semi-molten PLA resin, forminga plurality of drawn PLA continuous filaments, depositing the pluralityof PLA continuous filaments onto a collection surface, exposing theplurality of PLA continuous filaments to ions, and bonding the pluralityof PLA continuous filaments to form the PLA spunbond nonwoven fabric.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a schematic diagram of the PLA spunbond nonwoven fabricpreparation system in accordance with certain embodiments of theinvention;

FIGS. 2A-2C are schematic diagrams illustrating positioning of the firstionization source in accordance with certain embodiments of theinvention;

FIGS. 3A-3C illustrate fibers formed by the PLA spunbond nonwoven fabricpreparation system in accordance with certain embodiments of theinvention;

FIGS. 4A-4D illustrate bond patterns used with the PLA spunbond nonwovenfabric preparation system in accordance with certain embodiments of theinvention;

FIG. 5 is a block diagram of a process for preparing the PLA spunbondnonwoven fabric in accordance with certain embodiments of the invention;and

FIG. 6 is a block diagram of the process for forming PLA continuousfilaments in accordance with the process illustrated in the blockdiagram of FIG. 5.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout. As used inthe specification, and in the appended claims, the singular forms “a”,“an”, “the”, include plural referents unless the context clearlydictates otherwise.

The invention includes, according to certain embodiments, systems andprocesses for preparing polylactic acid (PLA) spunbond nonwoven fabricsat high speeds. In particular, embodiments of the invention are directedto systems and processes that utilize means for controlling static,including ionization sources, to prepare PLA spunbond nonwoven fabric.In this regard, PLA processing can occur at high speeds with minimalwaste, thereby making spunbond PLA production economically attractive.

PLA spunbond nonwoven fabrics made by systems and processes inaccordance with embodiments of the invention may be used in a widevariety of applications, including diapers, feminine care products,incontinence products, agricultural products (e.g., root wraps, seedbags, crop covers and/or the like), industrial products (e.g. work wearcoveralls, airline pillows, automobile trunk liner and sound proofing),and household products (e.g., furniture scratch pads, mattress coilcovers and/or the like).

I. Definitions

For the purposes of the present application, the following terms shallhave the following meanings:

The term “fiber” can refer to a fiber of finite length or a filament ofinfinite length.

As used herein, the term “monocomponent” refers to fibers formed fromone polymer or formed from a single blend of polymers. Of course, thisdoes not exclude fibers to which additives have been added for color,anti-static properties, lubrication, hydrophilicity, liquid repellency,etc.

As used herein, the term “multicomponent” refers to fibers formed fromat least two polymers (e.g., bicomponent fibers) that are extruded fromseparate extruders. The at least two polymers can each independently bethe same or different from each other, or be a blend of polymers. Thepolymers are arranged in substantially constantly positioned distinctzones across the cross-section of the fibers. The components may bearranged in any desired configuration, such as sheath-core,side-by-side, pie, island-in-the-sea, and so forth. Various methods forforming multicomponent fibers are described in U.S. Pat. No. 4,789,592to Taniguchi et al. and U.S. Pat. No. 5,336,552 to Strack et al., U.S.Pat. No. 5,108,820 to Kaneko, et al., U.S. Pat. No. 4,795,668 to Kruege,et al., U.S. Pat. No. 5,382,400 to Pike, et al., U.S. Pat. No. 5,336,552to Strack, et al., and U.S. Pat. No. 6,200,669 to Marmon, et al., whichare incorporated herein in their entirety by reference. Multicomponentfibers having various irregular shapes may also be formed, such asdescribed in U.S. Pat. No. 5,277,976 to Hogle, et al., U.S. Pat. No.5,162,074 to Hills, U.S. Pat. No. 5,466,410 to Hills, U.S. Pat. No.5,069,970 to Largman, et al., and U.S. Pat. No. 5,057,368 to Largman, etal., which are incorporated herein in their entirety by reference.

As used herein, the terms “nonwoven,” “nonwoven web” and “nonwovenfabric” refer to a structure or a web of material which has been formedwithout use of weaving or knitting processes to produce a structure ofindividual fibers or threads which are intermeshed, but not in anidentifiable, repeating manner. Nonwoven webs have been, in the past,formed by a variety of conventional processes such as, for example,meltblown processes, spunbond processes, and staple fiber cardingprocesses.

As used herein, the term “meltblown” refers to a process in which fibersare formed by extruding a molten thermoplastic material through aplurality of fine, usually circular, die capillaries into a highvelocity gas (e.g. air) stream which attenuates the molten thermoplasticmaterial and forms fibers, which can be to microfiber diameter.Thereafter, the meltblown fibers are carried by the gas stream and aredeposited on a collecting surface to form a web of random meltblownfibers. Such a process is disclosed, for example, in U.S. Pat. No.3,849,241 to Buntin et al.

As used herein, the term “machine direction” or “MD” refers to thedirection of travel of the nonwoven web during manufacturing.

As used herein, the term “cross direction” or “CD” refers to a directionthat is perpendicular to the machine direction and extends laterallyacross the width of the nonwoven web.

As used herein, the term “spunbond” refers to a process involvingextruding a molten thermoplastic material as filaments from a pluralityof fine, usually circular, capillaries of a spinneret, with thefilaments then being attenuated and drawn mechanically or pneumatically.The filaments are deposited on a collecting surface to form a web ofrandomly arranged substantially continuous filaments which canthereafter be bonded together to form a coherent nonwoven fabric. Theproduction of spunbond non-woven webs is illustrated in patents such as,for example, U.S. Pat. Nos. 3,338,992; 3,692,613, 3,802,817; 4,405,297and 5,665,300. In general, these spunbond processes include extrudingthe filaments from a spinneret, quenching the filaments with a flow ofair to hasten the solidification of the molten filaments, attenuatingthe filaments by applying a draw tension, either by pneumaticallyentraining the filaments in an air stream or mechanically by wrappingthem around mechanical draw rolls, depositing the drawn filaments onto aforaminous collection surface to form a web, and bonding the web ofloose filaments into a nonwoven fabric. The bonding can be any thermalor chemical bonding treatment, with thermal point bonding being typical.

As used herein, the term “thermal point bonding” involves passing amaterial such as one or more webs of fibers to be bonded between aheated calender roll and an anvil roll. The calender roll is typicallypatterned so that the fabric is bonded in discrete point bond sitesrather than being bonded across its entire surface.

As used herein, the term “polymer” generally includes, but is notlimited to, homopolymers, copolymers, such as, for example, block,graft, random and alternating copolymers, terpolymers, etc. and blendsand modifications thereof. Furthermore, unless otherwise specificallylimited, the term “polymer” shall include all possible geometricalconfigurations of the material, including isotactic, syndiotactic andrandom symmetries.

II. System for Preparing PLA Spunbond Nonwoven Fabrics

Certain embodiments according to the invention provide systems forpreparing a polylactic acid (PLA) spunbond nonwoven fabric. Inaccordance with certain embodiments, the system includes a first PLAsource configured to provide a stream of molten or semi-molten PLAresin, a spin beam in fluid communication with the first PLA source, acollection surface disposed below an outlet of the spin beam onto whichthe PLA continuous filaments are deposited to form the PLA spunbondnonwoven fabric, a first ionization source positioned and arranged toexpose the PLA continuous filaments to ions, and a calender positioneddownstream of the first ionization source. The spin beam, according tocertain embodiments, is configured to extrude and draw a plurality ofPLA continuous filaments.

In this regard, the spunbond nonwoven web may be produced, for example,by the conventional spunbond process on spunbond machinery such as, forexample, the Reicofil-3 line or Reicofil-4 line from Reifenhauser, asdescribed in U.S. Pat. No. 5,814,349 to Geus et al, the entire contentsof which are incorporated herein by reference, wherein molten polymer isextruded into continuous filaments which are subsequently quenched,attenuated pneumatically by a high velocity fluid, and collected inrandom arrangement on a collecting surface. In some embodiments, thecontinuous filaments are collected with the aid of a vacuum sourcepositioned below the collection surface. After filament collection, anythermal, chemical or mechanical bonding treatment may be used to form abonded web such that a coherent web structure results. As one skilled inthe art will understand, examples of thermal bonding may includethru-air bonding where hot air is forced through the web to soften thepolymer on the outside of certain fibers in the web followed by at leastlimited compression of the web or calender bonding where the web iscompressed between two rolls, at least one of which is heated, andtypically one is an embossed roll.

In some embodiments, for instance, the collection surface may compriseconductive fibers. The conductive fibers may comprise monofilament wiresmade from polyethersulfone conditioned with polyamide (e.g., Huycon—LX135). In the machine direction, the fibers comprise polyamideconditioned polyethersulfone. In the cross-machine direction, the fiberscomprise polyamide conditioned polyethersulfone in combination withadditional polyethersulfone.

With reference to FIG. 1, for example, a schematic diagram of the PLAspunbond nonwoven fabric preparation system in accordance with certainembodiments of the invention is illustrated. As shown in FIG. 1, the PLAsource (i.e. hopper) 42 is in fluid communication with the spin beam 19via the extruder 43. Although FIG. 1 illustrates an embodiment havingtwo PLA sources 42 and two extruders 43, the system may include anynumber of polymer sources (e.g., PLA, synthetic polymer, such aspolypropylene, polyethylene, etc.) and extruders as dictated by aparticular application as understood by one of ordinary skill in theart. Following extrusion, the extruded polymer may then enter aplurality of spinnerets (not shown) for spinning into filaments.Following spinning, the spun filaments may then be drawn (i.e.attenuated) via a drawing unit (not shown) and randomized in a diffuser(46 in FIGS. 2A-2C). The spin beam 19 produces a curtain of filaments(47 in FIGS. 2A-2C) that is deposited on the collection surface 10 atpoint 45.

In one embodiment, the thus deposited filaments may then be bonded toform a coherent web. In some embodiments, a pair of cooperating rolls 12(also referred to herein as a “press roll”) stabilize the web of the PLAcontinuous filaments by compressing said web before delivery to thecalender 28 for bonding. In some embodiments, for example, the pressroll may include a ceramic coating deposited on a surface thereof. Incertain embodiments, for instance, one roll of the pair of cooperatingrolls 12 may be positioned above the collection surface 10, and a secondroll of the pair of cooperating rolls 12 may be positioned below thecollection surface 10. Finally, the bonded PLA spunbond nonwoven fabricmoves to a winder 29, where the fabric is wound onto rolls.

During the course of their investigation, the inventors have discoveredthat static generation during fiber spinning and web processing when PLAis exposed on the fiber surface promotes web wraps at the press rollsand calender of the spunbond machine. This web wrap is undesirable andgenerally has prevented the high speed production of fabrics comprising100% PLA, or fabrics in which PLA is exposed at the surface of thefibers. One method of addressing web wrap is by increasing the humidityof the spunbond process by, for example, injecting steam into the airstream used to quench the just-spun fibers or providing a fine mist orfog of moisture around the press rolls where the spun fibers are firstformed into an unbonded web. Although the extra humidity provides someprotection from web wraps, the addition of high moisture over a periodof time may promote corrosion of the spunbond machine and growth of moldor microorganisms detrimental to nonwoven use in hygiene and medicaloperations.

Another method of reducing static charge build up in the nonwoven fabricis to contact the web where the PLA is exposed on the surface of thefiber with a conductive static bar, which helps to ground the web,thereby dissipating charge build-up. However, this approach requiresdirect contact between the nonwoven web and the conductive substrate,and at such contact points there remains the possibility of directdischarge of static electricity through space with resulting possibleharm to the operator, damage to equipment and risk of fire.

Advantageously, the inventors have discovered that fabrics comprising100% PLA may be prepared at commercially viable processing speeds bypositioning one or more ionization sources in close proximity to thenonwoven fabric. For example, in one embodiment, an ionization source 26may be positioned near the spin beam 19 and the winder 29 to activelydissipate/neutralize static charge without contacting the fabric. Asexplained below, the ionization source exposes the nonwoven fabric to astream of ions, which act to neutralize static charges in the nonwovenfabric. The stream of ions may include positive ions, negative ions, andcombinations thereof.

In some embodiments, it may also be desirable to position a staticcontrol unit 27 near the calender 28. The static control unit 27 may bea passive static bar requiring contact with the fabric or an activeionization bar, which does not require contact with the fabric. Finally,an optional humidity unit 44 may be used in conjunction with the spinbeam 19 and/or the press roll 12 to reduce static via added moisture.

In accordance with certain embodiments, for example, the firstionization source may be positioned above the collection surface anddownstream of a point at where the PLA continuous filaments aredeposited on the collection surface. However, in other embodiments, forinstance, the first ionization source may be positioned between theoutlet of the spin beam and the collection surface.

As discussed previously, the system may further comprise a press rollpositioned downstream from the outlet of the spin beam. In this regard,the press roll may be configured to stabilize the web of the PLAcontinuous filaments by compressing said web before delivery of the PLAcontinuous fibers from the outlet of the spin beam towards the calender.In those embodiments including the press roll, for example, the firstionization source may be positioned downstream from the press roll. Inother embodiments, for instance, the first ionization source may bepositioned between the spin beam and the press roll.

In some embodiments and as shown in FIG. 1, the system may comprise avacuum source 14 disposed below the collection surface for pulling theplurality of PLA continuous filaments from the outlet of the spin beamonto the collection surface before delivery to the calender.

FIGS. 2A-2C, for example, are schematic diagrams illustratingpositioning of the first ionization source in accordance with certainembodiments of the invention. As shown in FIG. 2A, the first ionizationsource 26 is positioned downstream of the outlet (i.e. diffuser) 46 ofthe spin beam 19 but upstream of the press roll 12. In FIG. 2B, however,the first ionization source 26 is positioned downstream of the pressroll 12. In FIG. 2C, the first ionization source is positioneddownstream of the point 45 at which the curtain of filaments 47 aredeposited on the collection surface but also within the outlet 46.

Preferably, the ionization source comprises a device that is capable ofactively discharging ions with the use of electrodes, ionizing airnozzles, ionizing air blowers, and the like. In one embodiment, theionization source comprises an active discharge ionization bar thatactively discharges ions in the direction of the nonwoven fabric.Examples of suitable ionization bars may include ElektrostatikDischarging Electrode E3412, which is available from Iontis.

In one embodiment, the ionization bar may extend over the web in thecross direction. Preferably, the ionization bar extends in the crossdirection across the total width of the nonwoven fabric. In furtherembodiments, the ionization bar may extend under the web and thecollection surface in the cross direction. However, positioning theionization bar under the collection surface may be less effective thanpositioning the ionization bar over the web in the cross direction.

According to certain embodiments, for example, the first ionizationsource and the collection surface may be separated by a distance fromabout 1 inch to about 24 inches. In other embodiments, for instance, thefirst ionization source and the collection surface may be separated by adistance from about 1 inch to about 12 inches. In further embodiments,for example, the first ionization source and the collection surface maybe separated by a distance from about 1 inch to about 5 inches. As such,in certain embodiments, the first ionization source and the collectionsurface may be separated by a distance from at least about any of thefollowing: 1, 1.25, 1.5, 1.75, and 2 inches and/or at most about 24, 20,16, 12, 10, 9, 8, 7, 6, and 5 inches (e.g., about 1.5-10 inches, about2-8 inches, etc.).

In accordance with certain embodiments, for instance, the system mayfurther comprise a static control unit positioned and arranged todissipate static from the PLA spunbond nonwoven fabric proximate to thecalender. In some embodiments, for example, the static control unit maybe positioned upstream from, and adjacent to, the calender. In otherembodiments, however, the static control unit may be positioneddownstream from, and adjacent to, the calender.

In some embodiments, for instance, the static control unit may comprisea passive static bar. In such embodiments, the static control unit maycontact the PLA spunbond nonwoven fabric in order to dissipate staticcharge. In other embodiments, however, the static control unit maycomprise a second ionization source. As such, the second ionizationsource may actively dissipate static charge from the PLA spunbondnonwoven fabric such that contact by the second ionization source withthe PLA spunbond nonwoven fabric is not required in order to dissipatethe static charge.

According to certain embodiments, for example, the system may furthercomprise a winder positioned downstream from the calender. In suchembodiments, for instance, the system may also include a thirdionization source positioned and arranged to expose the PLA spunbondnonwoven fabric to ions proximate to the winder. In some embodiments,for example, at least one of the first ionization source, the staticcontrol source (e.g., the second ionization source), and the thirdionization source may comprise an ionization bar. In this regard, forinstance, the first ionization source, the static control source, andthe third ionization source may be configured to actively dissipatestatic charge created during preparation of the PLA spunbond nonwovenfabric.

In accordance with certain embodiments, for example, the system mayfurther comprise a humidity unit positioned within or downstream fromthe spin beam. In such embodiments, for instance, the humidity unit maycomprise at least one of a steam unit, a fogging unit, a misting unit,or any combination thereof. In this regard, for example, humidity may beadded in the spin beam during the formation of the plurality of PLAcontinuous filaments and/or near the press roll(s) (in those embodimentsutilizing at least one press roll) in order to provide additionalmanagement of static charge that develops during the production of thePLA spunbond nonwoven fabric.

In accordance with certain embodiments, for instance, the system may beconfigured to prepare the PLA continuous fibers at a fiber draw speedgreater than about 2500 in/min. In other embodiments, for example, thesystem may be configured to prepare the PLA continuous fibers at a fiberdraw speed from about 3000 in/min to about 4000 in/min. In furtherembodiments, for instance, the system may be configured to prepare thePLA continuous fibers at a fiber draw speed from about 3000 in/min toabout 5500 in/min. As such, in certain embodiments, the system may beconfigured to prepare the PLA continuous fibers at a fiber draw speedfrom at least about any of the following: 2501, 2550, 2600, 2650, 2700,2750, 2800, 2850, 2900, 2950, and 3000 in/min and/or at most about 5500,4000, 3950, 3900, 3850, 3800, 3750, 3700, 3650, 3600, 3550, and 3500in/min (e.g., about 2700-3800 in/min, about 3000-3700 in/min, etc.).Such speeds are merely exemplary, as the system may be run at fiber drawspeeds slower than 2500 in/min as well. However, use of fiber draw speedsignificantly below 2500 in/min may begin to compromise fabricproperties such as strength and resistance to shrinkage.

In accordance with certain embodiments, for instance those embodimentsinvolving the manufacture of spunbond fabrics having a basis weight fromabout 8 g/m2 to about 70 g/m2, the system may be configured to preparethe bonded nonwoven web comprising PLA continuous fibers from one spinbeam in cooperation with a collector operating at a linear speed ofapproximately 50 to 450 in/min, or from two spin beams in cooperationwith a collector operating at a linear speed of approximately 100 to 900in/min, or from three spin beams in cooperation with a collectoroperating at a linear speed of approximately 150 to 1200 in/min. In thisregard, one of ordinary skill in the art would appreciate that thepolymer thru-put though the spinneret should generally coordinate withthe collector speed to achieve a desired spunbond basis weight.

In accordance with certain embodiments, for example, the calender maycomprise a pair of cooperating rolls including a patterned roll. In suchembodiments, for instance, the patterned roll may comprise athree-dimensional geometric bonding pattern. In some embodiments, forexample, the bonding pattern may comprise at least one of a diamondpattern, a hexagonal dot pattern, an oval-elliptic pattern, a rod-shapedpattern, or any combination thereof. However, any pattern known in theart may be used with typical embodiments employing continuous ordiscontinuous patterns. In some embodiments, both rolls of the calenderroll may be patterned, or alternatively, one of the rolls may include apattern while the other roll comprises an anvil roll.

FIGS. 4A-4D, for example, illustrate bond patterns used with the PLAspunbond nonwoven fabric preparation system in accordance with certainembodiments of the invention. FIG. 4A illustrates a hexagonal dotpattern 60 a, FIG. 4B illustrates an oval-elliptic pattern 60 b, FIG. 4Cillustrates a rod-shaped pattern 60 c, and FIG. 4D illustrates a diamondpattern 60 d.

In certain embodiments, for instance, the bonding pattern may cover fromabout 5% to about 30% of the surface area of the patterned roll. Inother embodiments, for example, the bonding pattern may cover from about10% to about 25% of the surface area of the patterned roll. As such, incertain embodiments, the bonding pattern may cover from at least aboutany of the following: 5, 6, 7, 8, 9, and 10% and/or at most about 30,29, 28, 27, 26, and 25% (e.g., about 8-27%, about 10-30%, etc.). In someembodiments, for instance, the bonding pattern may comprise the diamondpattern, and the bonding pattern covers about 25% of the surface area ofthe patterned roll. In further embodiments, for example, the bondingpattern may comprise the oval-elliptic pattern, and the bonding patterncovers about 18% of the surface area of the patterned roll.

In some embodiments, the calender may include a release coating tominimize deposit of molten or semi molten polymer on the surfaces of oneor more of the rolls. As an example, such release coatings are describedin European Patent Applicant No. 1,432,860, which is incorporated hereinin its entirety by reference. In this regard, the release coating mayhelp prevent and reduce sticking of the nonwoven fabric to the calenderroll should molten polymer drips be released by spinning faults withinthe spin beam.

In accordance with certain embodiments, the PLA spunbond nonwoven fabricis substantially free of synthetic polymer components, such aspetroleum-based materials and polymers. For example, the PLA spunbondnonwoven fabric may have a monocomponent structure in which 100% of thefiber is PLA, or may have a bicomponent structure in which the bothcomponents are PLA based to thus produce a fiber that is 100% PLA.

As used herein, “100% PLA” may also include up to 5% additives includingadditives and/or masterbatches of additives to provide, by way ofexample only, color, softness, slip, antistatic protection, lubricity,hydrophilicity, liquid repellency, antioxidant protection and the like.In this regard, the nonwoven may comprise 95-100% PLA, such as from96-100% PLA, 97-100% PLA, 98-100% PLA, 99-100% PLA, etc. When suchadditives are added as a masterbatch, for instance, the masterbatchcarrier may primarily comprise PLA in order to facilitate processing andto maximize sustainable content within the formulation.

Generally, polylactic acid based polymers are prepared from dextrose, asource of sugar, derived from field corn. In North America corn is usedsince it is the most economical source of plant starch for ultimateconversion to sugar. However, it should be recognized that dextrose canbe derived from sources other than corn. Sugar is converted to lacticacid or a lactic acid derivative via fermentation through the use ofmicroorganisms. Lactic acid may then be polymerized to form PLA.Examples of such high performance PLA resins include L105, L130, L175,and LX175, all from Corbion of Arkelsedijk 46, 4206 A C Gorinchem, theNetherlands. Thus, besides corn other agricultural based sugar sourcecould be used including rice, sugar beets, sugar cane, wheat, cellulosicmaterials, such as xylose recovered from wood pulping, and the like.

In some embodiments, the nonwoven fabrics may be biodegradable.“Biodegradable” refers to a material or product which degrades ordecomposes under environmental conditions that include the action ofmicroorganisms. Thus, a material is considered as biodegradable if aspecified reduction of tensile strength and/or of peak elongation of thematerial or other critical physical or mechanical property is observedafter exposure to a defined biological environment for a defined time.Depending on the defined biological conditions, a fabric comprised ofPLA might or might not be considered biodegradable.

A special class of biodegradable products made with a bio-based materialmight be considered as compostable if it can be degraded in a composingenvironment. The European standard EN 13432, “Proof of Compostability ofPlastic Products” may be used to determine if a fabric or film comprisedof sustainable content could be classified as compostable.

In some embodiments, sustainable polymer components of biodegradableproducts may be derived from an aliphatic component possessing onecarboxylic acid group (or a polyester forming derivative thereof, suchas an ester group) and one hydroxyl group (or a polyester formingderivative thereof, such as an ether group) or may be derived from acombination of an aliphatic component possessing two carboxylic acidgroups (or a polyester forming derivative thereof, such as an estergroup) with an aliphatic component possessing two hydroxyl groups (or apolyester forming derivative thereof, such as an ether group).

The term “aliphatic polyester” covers—besides polyesters which are madefrom aliphatic and/or cycloaliphatic components exclusively alsopolyesters which contain besides aliphatic and/or cylcoaliphatic unitsaromatic units, as long as the polyester has substantial sustainablecontent. As noted above, the sustainable content is typically at least25 weight %, and more preferably 75 weight % and even more preferably atleast 90 weight %.

Polymers derived from an aliphatic component possessing one carboxylicacid group and one hydroxyl group are alternatively calledpolyhydroxyalkanoates (PHA). Examples thereof are polyhydroxybutyrate(PHB), poly-(hydroxybutyrate-co-hydroxyvaleterate) (PHBV),poly-(hydroxybutyrate-co-polyhydroxyhexanoate) (PHBH), polyglycolic acid(PGA), poly-(epsilon-caprolactione) (PCL) and preferably polylactic acid(PLA).

Examples of polymers derived from a combination of an aliphaticcomponent possessing two carboxylic acid groups with an aliphaticcomponent possessing two hydroxyl groups are polyesters derived fromaliphatic diols and from aliphatic dicarboxylic acids, such aspolybutylene succinate (PBSU), polyethylene succinate (PESU),polybutylene adipate (PBA), polyethylene adipate (PEA),polytetramethy-lene adipate/terephthalate (PTMAT).

In accordance with certain embodiments, for example, the nonwoven fabricmay comprise bicomponent fibers. In some embodiments, for instance, thebicomponent fibers may comprise a side-by-side arrangement. However, inother embodiments, for example, the bicomponent fibers may comprise asheath and a core. In some embodiments, the bicomponent fibers can bemade using sheath/core bicomponent fibers where the core comprises PLA,and the sheath comprises polymers including, but not limited to,polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET)and/or the like. However, in other embodiments, the nonwoven fabric maycomprise reverse bicomponent fibers where the core comprises polymersincluding, but not limited to, PP, PE, PET and/or the like, and thesheath comprises PLA.

In such embodiments, for instance, the sheath may comprise PLA. Infurther embodiments, for example, the core may comprise at least onesynthetic polymer component. For example, the PLA continuous filamentsmay comprise a PLA sheath, and a synthetic polymer, such as PP, PE, PET,or any combination thereof. In other embodiments, the core may comprisePLA in which the PLA may have a higher or lower melting temperature thanthe PLA of the sheath. In this regard, the bicomponent fibers maycomprise PLA/PP reverse bicomponent fibers, PLA/PE reverse bicomponentfibers, PLA/PET reverse bicomponent fibers, or PLA/PLA reversebicomponent fibers.

In certain embodiments, for instance, the bicomponent fibers maycomprise PLA/PLA reverse bicomponent fibers such that the sheathcomprises a first PLA grade, the core comprises a second PLA grade, andthe first PLA grade and the second PLA grade are different (e.g., thefirst PLA grade has a higher melting point than the second PLA grade).For example, in one embodiment, the core may comprise a PLA having alower % D isomer of polylactic acid than that of the % D isomer PLApolymer used in the sheath. The PLA polymer with lower % D isomer willshow higher degree of stress induced crystallization during spinningwhile the PLA polymer with higher D % isomer will retain a moreamorphous state during spinning. The more amorphous sheath will promotebonding while the core showing a higher degree of crystallization willprovide strength to the fiber and thus to the final bonded web. In oneparticular embodiment, the Nature Works PLA Grade PLA 6752 with 4% DIsomer can be used as the sheath while NatureWorks Grade 6202 with 2% DIsomer can be used as the core.

By way of example only, the sheath may comprise PLA; the core maycomprise at least one synthetic polymer component. The PLA grade of thestarting material should have proper molecular properties to be spun inspunbond processes. Examples of suitable include PLA grades suppliedfrom NatureWorks LLC, of Minnetonka, Minn. 55345 such as, grade 6752D,6100D, and 6202D believed to be produced as generally following theteaching of U.S. Pat. Nos. 5,525,706 and 6,807,973 both to Gruber et al.

Examples of synthetic polymer components include polyolefins, such as PPand PE, blends of polyolefins, such as those taught by Chester et al. inUS Patent Publication No. 2014/0276517 incorporated herein in itsentirety by reference, polyesters, such as PET, polytrimethyleneterephthalate (PIT), and polybutylene terephthalate (PBT), polystyrenes,and the like.

A wide variety of polypropylene polymers may be used in the startingmaterial including both polypropylene homopolymers and polypropylenecopolymers. In one embodiment, the polypropylene of the startingmaterial may comprise a metallocene or Ziegler Natta catalyzed propylenepolymers.

Examples of Ziegler Natta polypropylenes that may be used in embodimentsof the present invention include TOTAL®3866 polypropylene from TotalPetrochemicals USA, INC of Houston, Tex.; Braskem CP 360H polypropylenefrom Braskem America of Philadelphia, Pa.; ExxonMobil PD 3445 fromExxonMobil of Houston, Tex.; Sabic 511A from Sabic of Sittard, TheNetherlands; and Pro-fax PH 835 from Basell Polyolefins of Wilmington,Del. Examples of suitable metallocene polypropylenes may include TOTAL®M3766 polypropylene from Total Petrochemicals USA, INC of Houston, Tex.;TOTAL® MR 2001 polypropylene from Total S.A. of Courbevoie, France;ACHIEVE® 3754 polypropylene from ExxonMobil of Houston, Tex.; andACHIEVE® 3825 polypropylene from ExxonMobil of Houston, Tex.

For example, in one embodiment, the system may be configured to producea nonwoven comprising a PLA sheath and a polyolefin core.

In some embodiments, the system may be configured to prepare the PLAspunbond nonwoven fabric at a fiber draw speed from about 3000 m/min toabout 5500 m/min. In other embodiments, for instance, each of the sheathand the core may comprise PLA, and the system may be configured toprepare the PLA spunbond nonwoven fabric at a fiber draw speed fromabout 3000 m/min to about 4000 m/min.

However, in other embodiments, for example, the nonwoven fabric maycomprise PLA monocomponent fibers. In this regard, the nonwoven fabricmay be 100% PLA.

FIGS. 3A-3C, for example, illustrate fibers formed by the PLA spunbondnonwoven fabric preparation system in accordance with certainembodiments of the invention. As shown in FIG. 3A, the fiber may be asheath/core bicomponent fiber 52 having a sheath 53 and a core 54, asmore fully described above. FIG. 3B illustrates a side-by-sidebicomponent fiber 55 having a first continuous polymer 56 and a secondcontinuous polymer 57. Finally, FIG. 3C illustrates a monocomponentfiber 58.

According to certain embodiments, the PLA spunbond nonwoven fabriccomprises a spunbond fabric or a spunbond-meltblown-spunbond (SMS)fabric. In certain embodiments in which the PLA spunbond nonwoven fabriccomprises a SMS fabric, the spunbond nonwoven layer may comprisebicomponent fibers having a PLA sheath and a PLA core, and a meltblownlayer comprising PLA fibers. In such embodiments, each of the spunbondand meltblown layers may comprise PLA on the surface of the fibers. Anexample of a suitable PLA material for use as the sheath is PLA grade6752 with 4% D Isomer, and an example of a suitable PLA material for useas the core is PLA grade 6202 with 2% D Isomer, both of which areavailable from NatureWorks. A suitable material for the PLA meltblownfibers is PLA grade 6252, which is also available from NatureWorks.

III. Process for Preparing PLA Spunbond Nonwoven Fabrics

In another aspect, certain embodiments according to the inventionprovide processes for preparing a PLA spunbond nonwoven fabric. Inaccordance with certain embodiments, the process includes providing astream of molten or semi-molten PLA resin, forming a plurality of drawnPLA continuous filaments, depositing the plurality of PLA continuousfilaments onto a collection surface, exposing the plurality of PLAcontinuous filaments to ions, and bonding the plurality of PLAcontinuous filaments to form the PLA spunbond nonwoven fabric.

FIG. 5, for example, is a block diagram of a process for preparing thePLA spunbond nonwoven fabric in accordance with certain embodiments ofthe invention. As shown in FIG. 5, the process 70 includes providing astream of molten or semi-molten PLA resin at operation 71, forming aplurality of drawn PLA continuous filaments at operation 72, an optionalstep of increasing humidity during the forming step at operation 79,depositing the plurality of PLA continuous filaments onto a collectionsurface at operation 73 where said depositing step 73 is often aided bya vacuum box under said collection surface, exposing the plurality ofPLA continuous filaments to ions at operation 74, bonding the pluralityof PLA continuous filaments to form the PLA spunbond nonwoven fabric atoperation 75, and an optional step of dissipating static charge from thePLA spunbond nonwoven fabric before or after the bonding step atoperation 80. In addition, the process 70 includes the optional steps ofcutting the PLA spunbond nonwoven fabric to form cut PLA spunbondnonwoven fabric at operation 76, actively dissipating static charge fromthe cut PLA spunbond nonwoven fabric at operation 77, and winding thecut PLA spunbond nonwoven fabric into rolls at operation 78.

According to certain embodiments, for example, forming the plurality ofattenuated or drawn PLA continuous filaments may comprise spinning theplurality of PLA continuous filaments, drawing the plurality of PLAcontinuous filaments, and randomizing the plurality of PLA continuousfilaments. FIG. 6, for example, is a block diagram of the process forforming drawn PLA continuous filaments in accordance with the processillustrated in the block diagram of FIG. 5. As shown in FIG. 6, theforming step 71 includes spinning the plurality of PLA continuousfilaments at operation 81, drawing the plurality of PLA continuousfilaments at operation 82, and randomizing the plurality of PLAcontinuous filaments at operation 83.

In this regard, the spunbond nonwoven web may be produced, for example,by the conventional spunbond process wherein molten polymer is extrudedinto continuous filaments which are subsequently quenched, attenuated ordrawn mechanically by draw rolls or pneumatically by a high velocityfluid, and collected in random arrangement on a collecting surface.After filament collection, any thermal, chemical or mechanical bondingtreatment may be used to form a bonded web such that a coherent webstructure results.

In accordance with certain embodiments, for instance, the system may beconfigured to prepare the PLA continuous fibers at a fiber draw speedgreater than about 2500 in/min. In other embodiments, for example, thesystem may be configured to prepare the PLA continuous fibers at a fiberdraw speed from about 3000 in/min to about 4000 in/min. In furtherembodiments, for instance, the system may be configured to prepare thePLA continuous fibers at a fiber draw speed from about 3000 in/min toabout 5500 in/min. As such, in certain embodiments, the system may beconfigured to prepare the PLA continuous fibers at a fiber draw speedfrom at least about any of the following: 2501, 2550, 2600, 2650, 2700,2750, 2800, 2850, 2900, 2950, and 3000 in/min and/or at most about 5500,4000, 3950, 3900, 3850, 3800, 3750, 3700, 3650, 3600, 3550, and 3500in/min (e.g., about 2700-3800 in/min, about 3000-3700 in/min, etc.).Such speeds are merely exemplary, as the system may be run at fiber drawspeeds slower than 2500 in/min as well. However use of fiber draw speedsignificantly below 2500 in/min may begin to compromise fabricproperties such as strength and resistance to shrinkage.

In accordance with certain embodiments, for instance those embodimentsinvolving the manufacture of spunbond fabrics having a basis weight fromabout 8 g/m2 to about 70 g/m2, the system may be configured to preparethe bonded nonwoven web comprising PLA continuous fibers from one spinbeam in cooperation with a collector operating at a linear speed ofapproximately 50 to 450 in/min, or from two spin beams in cooperationwith a collector operating at a linear speed of approximately 100 to 900in/min, or from three spin beams in cooperation with a collectoroperating at a linear speed of approximately 150 to 1200 in/min. In thisregard, one of ordinary skill in the art would appreciate that thepolymer thru-put though the spinneret should generally coordinate withthe collector speed to achieve a desired spunbond basis weight.

In accordance with certain embodiments, for example, forming theplurality of PLA continuous filaments may comprise forming bicomponentfibers. In some embodiments, for instance, forming bicomponent fibersmay comprise forming side-by-side bicomponent fibers. In otherembodiments, however, forming bicomponent fibers may comprise formingbicomponent fibers having a sheath and a core. In such embodiments, forexample, the sheath may comprise PLA. In further embodiments, forinstance, the core may comprise at least one different polymercomponent, such as polypropylene, polyethylene, polyethyleneterephthalate, PLA, and the like, or any combination thereof. In certainembodiments, for example, the bicomponent fibers may comprise PLA suchthat the sheath may comprise a first PLA grade, the core may comprise asecond PLA grade, and the first PLA grade and the second PLA grade maybe different. In further embodiments, for instance, the sheath maycomprise PLA, the core may comprise at least one of polypropylene,polyethylene, or polyethylene terephthalate, and the process may occurat a fiber draw speed of about 3000 in/min. In other embodiments, forexample, each of the sheath and the core may comprise PLA, and theprocess may occur at a fiber draw speed of about 3500 in/min or a fiberdraw speed of about 4000 in/min or even at a fiber draw speed of nearly5500 in/min.

However, in other embodiments, for instance, the nonwoven fabric maycomprise PLA monocomponent fibers. According to certain embodiments, forexample, the PLA spunbond nonwoven fabric may comprise a spunbond fabricor a spunbond-meltblown-spunbond (SMS) fabric. In embodiments in whichthe PLA spunbond nonwoven fabric comprises an SMS fabric, each of thespunbond and meltblown layers may comprise PLA on the surface of theirrespective fibers.

In accordance with certain embodiments, for instance, bonding the web toform the PLA spunbond nonwoven fabric may comprise thermal point bondingthe web with heat and pressure via a calender having a pair ofcooperating rolls including a patterned roll. In such embodiments, forexample, thermal point bonding the web may comprise imparting athree-dimensional geometric bonding pattern onto the PLA spunbondnonwoven fabric. In some embodiments, for instance, imparting thebonding pattern onto the PLA spunbond nonwoven fabric may compriseimparting at least one of a diamond pattern, a hexagonal dot pattern, anoval-elliptic pattern, a rod-shaped pattern, or any combination thereof.

In certain embodiments, for example, the bonding pattern may cover fromabout 5% to about 30% of the surface area of the patterned roll. Inother embodiments, for instance, the bonding pattern may cover fromabout 10% to about 25% of the surface area of the patterned roll. Assuch, in certain embodiments, the bonding pattern may cover from atleast about any of the following: 5, 6, 7, 8, 9, and 10% and/or at mostabout 30, 29, 28, 27, 26, and 25% (e.g., about 8-27%, about 10-30%,etc.). By way of example only, the bonding pattern may comprise thediamond pattern, and the bonding pattern may cover about 25% of thesurface area of the patterned roll. In further embodiments, forinstance, the bonding pattern may comprise the oval-elliptic pattern,and the bonding pattern may cover about 18% of the surface area of thepatterned roll. In some embodiments, for example, the calender maycomprise a release coating. As understood by one of ordinary skill inthe art, the nonwoven strength resulting from calendar bonding is acomplex function of the % area covered by the bond, temperature of thecalender rolls, compression pressure of the rolls against the web ofcontinuous fibers comprised of PLA, and the speed of the web through thecalendar.

In accordance with certain embodiments, for instance, the process mayfurther comprise dissipating static charge from the PLA spunbondnonwoven fabric proximate to the calender via the static control unit.In some embodiments, for example, the static control unit may comprise asecond ionization source. In further embodiments, for instance, thesecond ionization unit may comprise an ionization bar. However, in otherembodiments, for example, dissipating static charge from the PLAspunbond nonwoven fabric may comprise contacting the PLA spunbondnonwoven fabric with a static bar.

In accordance with certain embodiments, for instance, the process mayfurther comprise cutting the PLA spunbond nonwoven fabric to form cutPLA spunbond nonwoven fabric, exposing the cut PLA spunbond nonwovenfabric to ions via a third ionization source, and winding the cut PLAspunbond nonwoven fabric into rolls. In such embodiments, for example,the third ionization unit may comprise an ionization bar.

In accordance with certain embodiments, for instance, the process mayfurther comprise increasing humidity while forming the plurality of PLAcontinuous filaments. In such embodiments, for example, increasinghumidity may comprise applying at least one of steam, fog, mist, or anycombination thereof to the plurality of PLA continuous filaments.

Fabrics prepared in accordance with embodiments of the invention mayhave a wide variety of basis weight ranges depending on the desiredapplication. For example, fabrics and laminates incorporating thespunbond webs discussed herein may have basis weights ranging from about7 to 150 gsm, and in particular, from about 8 to 70 gsm. In someembodiments, the spunbond webs may have basis weights ranging from 10 to50 gsm, for example, from about 11 to 30 gsm.

Moreover, fabrics prepared in accordance with embodiments of theinvention may be characterized by an area shrinkage of less than 5%. Infurther embodiments, for example, the fabrics may be characterized by anarea shrinkage of less than 2%. In accordance with embodiments of theinvention, the ionization source may permit faster fiber draw speeds,which results may result in lower shrinkage.

Fabrics prepared in accordance with embodiments of the invention may beused in wide variety of applications including diapers, feminine careproducts, incontinence products, agricultural products (e.g., rootwraps, seed bags, crop covers and/or the like), industrial products(e.g. work wear coveralls, airline pillows, automobile trunk liner andsound proofing), and household products (e.g., furniture scratch pads,mattress coil covers and/or the like). In these applications, the fabricmay be incorporated into a multilayered structure.

In addition, spunbond webs prepared in accordance with embodiments ofthe present invention may be used in the production in a variety ofdifferent multilayer structures included meltblown/spunbond (MS)laminates, spunbond/meltblown/spunbond (SMS) laminates, andspunbond/meltblown/meltbown/spunbond (SMMS) laminates, for example. Inthese multilayer structures, the basis weight may range from as low asabout 7 g/m2 and up to about 150 g/m2. In such multilayered laminates,both the meltblown and spunbond fibers could have PLA polymer on thesurface to insure optimum bonding.

In some embodiments in which the spunbond layer is a part of amultilayer structure (e.g., MS, SMS, and SMMS), the amount of thespunbond in the structure may range from about 5 to 30% and inparticular, from about 10 to 25% of the structure as a percentage of thestructure as a whole.

In addition, spunbond webs in accordance with embodiments of the presentinvention may also be used in industrial applications including filters,cleaning products, “pigs” to absorb spilt oil or (if treated withsurfactant) to absorb contaminated materials from water, and the like.In these applications, the spunbond webs may have higher basis weightranges that may range from about 20 to 80 g/m2.

Multilayer structures in accordance with embodiments can be prepared ina variety of manners including continuous in-line processes where eachlayer is prepared in successive order on the same line, or depositing ameltblown layer on a previously formed spunbond layer. The layers of themultilayer structure can be bonded together to form a multilayercomposite sheet material using thermal bonding, mechanical bonding,adhesive bonding, hydroentangling, or combinations of these. In certainembodiments, the layers are thermally point bonded to each other bypassing the multilayer structure through a pair of calender rolls.

EXAMPLES

The following examples are provided for illustrating one or moreembodiments of the present invention and should not be construed aslimiting the invention.

Nonwoven fabrics in the following examples were prepared via aReifenhaeuser Reicofil-3 line or Reicofil-4 line. Each of the exampleswere prepared using the setup described in Example 1 unless otherwiseindicated. Moreover, unless otherwise indicated all percentages areweight percentages. The materials used in the examples are identifiedbelow.

Test Methods

Titer was calculated from microscopic measurement of fiber diameter andknown polymer density per German textile method C-1570.

Basis Weight was determined generally following the German textilemethod CM-130 from the weight of 10 layers of fabric cut into 10×10 cmsquares.

Tensile was determined in accordance with Method 10 DIN 53857 using asample with 5 cm width, 100 mm gauge length, and cross-head speed of 200min/min.

Elongation was determined in accordance with Method 10 DIN 53857 using asample with 5 cm width, 100 mm gauge length, and cross-head speed of 200min/min.

Fabric Shrinkage was determined by cutting three samples taken acrossthe web width of nominal dimensions of MD of 29.7 cm and CD of 21.0 cm;measuring the actual MD and CD width at three locations in the sheet;placing the sample in water heated to 60 C for 1 minute; and remeasuringthe MD and CD dimensions at the above three locations. The average widthmeasurement after exposure divided by the original measurement×100%yielded the % Shrinkage. A low % shrinkage value suggests that thecontinuous fibers comprising PLA have been spun and drawn at sufficientspeed to yield after bonding a high strength stable fabric.

Example 1

Example 1 was related to the production of PP/PLA bicomponent nonwovenwebs made using a Reicofil-3 beam and both R-3 and R-4 press rolls suchthat after lay-down and compression from the R-3 press roll, the webtraversed some distance on the collection surface and go under the R-4press roll before moving to the bonding station comprising the smoothand embossing rolls of the calender. The web was a 50/50 bicomponentnonwoven web with the sheath being LyondellBasell Z/N HP561R PP and thecore 6202D PLA from NatureWorks. The web was produced using spin beamtemperatures of 235° C. at the extruder and 240° C. at the die, a fiberdraw speed of 2700 in/min, and a line speed of 149 in/min. The calenderhad a diamond bonding pattern covering 25% of the surface area of thepattern roll, a calender temperature of 150° C. for each of the patternroll and the anvil roll, and a calender pressure of 70 N/mm. A passivestatic bar was positioned approximately 8-12 inches downstream of thecalender.

The nonwoven fabric of Example 1 was produced with one IonisElektrostatik Discharging Electrode E3412 (i.e. ionization bar)positioned above and extending over the collection surface in the crossdirection and placed approximately 1 to 3 inches above the collectionsurface and approximately 2 to 3 inches downstream from the R-3 pressroll. A second Ionis Elektrostatik Discharging Electrode E3412 (i.e.ionization bar) was placed in exactly the same corresponding positionabove the collection surface downstream of both the R-3 and the R-4press rolls. Both ionization bars were energized to insure that the webcomprising PLA fibers did not wrap either the R-3 press roll or the R-4press roll. A third Ionis Elektrostatik Discharging Electrode E3412(i.e. ionization bar) was placed between the calender and the winder toprotect the winder operators from electric shock when handling the cut(i.e. slit rolls) produced during the trial. Properties of Example 1 aresummarized in Tables 1 and 2 below.

Examples 2 and 3

Examples 2 and 3 were related to the production of spunbond fabrics withPLA on the fabric surface using a Reicofil-3 beam. The web was a reversebicomponent sheath/core 40/60 PLA/PP NatureWorks Grade6752/LyondellBasell HP561R PP produced using ionization bars. The websof Examples 2 and 3 were produced using spin beam temperatures of 235°C. at the extruder and 240° C. at the die, and a line speed of 149in/min. Example 2 was formed at a fiber draw speed of 2900 in/min. Thecalender for Example 2 had a diamond bonding pattern covering 25% of thesurface area of the pattern roll, calender temperatures of 160° C. forthe pattern roll and 125° C. for the anvil roll, and a calender pressureof 50 N/mm.

However, Example 3 was formed at a fiber draw speed of 3300 in/min, andthe calender for Example 3 had calender temperatures of 145° C. for thepattern roll and 125° C. for the anvil roll and a calender pressure of50 N/mm. Properties of Examples 2 and 3 are summarized in Tables 1 and 2below.

Examples 4 and 5

Examples 4 and 5 were related to the production of spunbond fabrics madeof 100% bicomponent PLA using a Reicofil-3 beam. The web was abicomponent sheath/core 40/60 NatureWorks Grade 6752/NatureWorks Grade6202 100% PLA using ionization bars and steam. The webs of Examples 4and 5 were produced using spin beam temperatures of 235° C. at theextruder and 240° C. at the die and a line speed of 119 in/min. Example4 was formed at a fiber draw speed of 3300 in/min. The calender forExample 4 had a diamond bonding pattern covering 25% of the surface areaof the pattern roll, had calender temperatures of 135° C. for thepattern roll and 125° C. for the anvil roll, and a calender pressure of70 N/mm.

However, Example 5 was formed at a fiber draw speed of 3500 in/min, andthe calender of Example 5 had calender temperatures of 140° C. for thepattern roll and 125° C. for the anvil roll and a calender pressure of70 N/mm. Properties of Examples 4 and 5 are summarized in Tables 1 and 2below.

Examples 6 and 7

Examples 6 and 7 were related to a bicomponent 100% PLA fabric madewithout using ionization bars or passive static bars but rather usingsteam added to the quench air to optimize moisture to minimize static.The fabrics were 100% bicomponent 50/50 Sheath/Core NatureWorks Grade6752/NatureWorks Grade 6202 using a Reicofil-4 beam. The web of Example6 was produced using spin beam temperatures of 230° C. for both theextruder and the die, a fiber draw speed of 3600 in/min, and a linespeed of 150 m/min. The calender for Example 6 had calender temperaturesof 139° C. for the pattern roll and 134° C. for the anvil roll and acalender pressure of 80 N/mm.

However, the web of Example 7 was produced using spin beam temperaturesof 235° C. for both the extruder and the die, a fiber draw speed of4100, and a line speed of 170 m/min. The calender for Example 7 hadcalender temperatures of 139° C. for the pattern roll and 134° C. forthe anvil roll and a calender pressure of 45 N/mm. Properties ofExamples 6 and 7 are summarized in Table 1 and 2 below.

Examples 8 and 9

Examples 8 and 9 were related to a 100% PLA bicomponent fabric made on aReicofil-4 beam. The setup differed from Example 1 in that one IonisElektrostatik Discharging Electrode E3412 (i.e. ionization bar) waspositioned above and extending over the collection surface in the crossdirection and placed approximately 1 to 3 inches above the collectionsurface and 2 to 3 inches downstream of the R-4 press roll. Because theR-4 spin beam was downstream of the R-3 spin beam, there was no concernabout wrapping the R-3 press roll. Accordingly, the ionization bar fromthe R-3 beam was de-energized during production of Examples 8 and 9.

The fabrics were bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. The webs of Examples 8 and 9 were produced at spin beamtemperatures of 235° C. at the extruder and 240° C. at the die. The webof Example 8 was produced at a fiber draw speed of 3600 in/min and aline speed of 145 m/min. The calender for Example 8 had calendertemperatures of 160° C. for the pattern roll and 147° C. for the anvilroll and a calender pressure of 40 N/mm.

However, the web of Example 9 was produced using a fiber draw speed of3800 m/min and a line speed of 90 m/min. The calender for Example 9 hadcalender temperatures of 160° C. for the pattern roll and 147° C. forthe anvil roll and a calender pressure of 40 N/mm. Properties ofExamples 8 and 9 are summarized in Tables 1 and 2 below.

TABLE 1 Nonwoven Mechanical Properties MD CD Tensile Tensile MD CD perBasis per Basis Toughness Toughness Basis MD Weight CD Weight MD % CD %Index Index Example Titer Weight Tensile N-sm/ Tensile N-sm/ Elong.Elong. Tensile X Tensile X Units DTEX g/m² N/5 cm g-5cm N/5 cm g-5cm % %% % 1 2.3 20.3 49.8 2.453 23.9 1.177 36.9 43.06 1838 1029 2 2.2 20.333.4 1.645 14.0 0.690 16.9 23.37 564 327 3 1.9 20.3 28.4 1.399 12.30.606 16.4 30.51 466 375 4 1.9 25.9 33.7 1.301 11.6 0.448 15.7 27.57 529320 5 1.8 25.9 37.9 1.463 14.8 0.571 19.0 29.66 720 439 6 1.94 24.8942.28 1.70 14.36 0.577 11.27 26.56 476 381 7 1.68 22.24 32.35 1.45 10.100.454 8.60 23.76 278 240 8 1.8 23.8 35.1 1.47 13.0 0.546 13.3 24.03 467312 9 1.7 39.8 70.7 1.78 26.6 0.668 14.7 28.61 1881 761

TABLE 2 Shrinkage Resistance for PLA Spunbond Fabric Example Shrink (MD)% Shrink (CD) % Area Shrink % 1 2.0 −0.1 1.9 2 2.2 −0.5 1.7 3 2.7 0.32.9 4 — — — 5 2.4 −1.7 0.7 6 — — — 7 — — — 8 3.1 −1.1 2.1 9 3.1 −1.4 1.8

NON-LIMITING EXEMPLARY EMBODIMENTS

Having described various aspects and embodiments of the inventionherein, further specific embodiments of the invention include those setforth in the following paragraphs.

Certain embodiments according to the invention provide systems forpreparing a polylactic acid (PLA) spunbond nonwoven fabric. Inaccordance with certain embodiments, the system includes a first PLAsource configured to provide a stream of molten or semi-molten PLAresin, a spin beam in fluid communication with the first PLA source, acollection surface disposed below an outlet of the spin beam onto whichthe PLA continuous filaments are deposited to form the PLA spunbondnonwoven fabric, a first ionization source positioned and arranged toexpose the PLA continuous filaments to ions, and a calender positioneddownstream of the first ionization source. The spin beam, according tocertain embodiments, is configured to extrude and draw a plurality ofPLA continuous filaments. Moreover, in some embodiments, the collectionsurface comprises conductive fibers.

In accordance with certain embodiments, the first ionization source ispositioned above the collection surface and downstream of a point atwhere the PLA continuous filaments are deposited on the collectionsurface. However, in other embodiments, the first ionization source ispositioned between the outlet of the spin beam and the collectionsurface. In certain embodiments, the system further comprises a pressroll positioned downstream from the outlet of the spin beam. In someembodiments, the first ionization source is positioned downstream fromthe press roll. In other embodiments, the first ionization source ispositioned between the spin beam and the press roll. However, in otherembodiments, the system further comprises a vacuum source disposed belowthe collection surface (i.e. in lieu of a press roll).

According to certain embodiments, the first ionization source and thecollection surface are separated by a distance from about 1 inch toabout 24 inches. In other embodiments, the first ionization source andthe collection surface are separated by a distance from about 1 inch toabout 12 inches. In further embodiments, the first ionization source andthe collection surface are separated by a distance from about 1 inch toabout 5 inches.

In accordance with certain embodiments, the system further comprises astatic control unit positioned and arranged to dissipate static from thePLA spunbond nonwoven fabric proximate to the calender. In someembodiments, the static control unit is positioned upstream from, andadjacent to, the calender. In other embodiments, however, the staticcontrol unit is positioned downstream from, and adjacent to, thecalender. In some embodiments, the static control unit comprises apassive static bar. In other embodiments, however, the static controlunit comprises a second ionization source.

According to certain embodiments, the system further comprises a winderpositioned downstream from the calender and a third ionization sourcepositioned and arranged to expose the PLA spunbond nonwoven fabric toions proximate to the winder. In some embodiments, at least one of thefirst ionization source, the static control source (e.g., the secondionization source), and the third ionization source comprises anionization bar extending over at least one of the plurality of PLAcontinuous filaments or the PLA spunbond nonwoven fabric in a crossdirection. In this regard, the first ionization source, the staticcontrol source, and the third ionization source are configured toactively dissipate static charge created during preparation of the PLAspunbond nonwoven fabric.

In accordance with certain embodiments, the system further comprises ahumidity unit positioned within or downstream from the spin beam. Insuch embodiments, the humidity unit comprises at least one of a steamunit, a fogging unit, a misting unit, or any combination thereof.

In accordance with certain embodiments, for instance, the system may beconfigured to prepare the PLA continuous fibers at a fiber draw speedgreater than about 2500 in/min. In other embodiments, for example, thesystem may be configured to prepare the PLA continuous fibers at a fiberdraw speed from about 3000 in/min to about 5500 in/min. In furtherembodiments, for instance, the system may be configured to prepare thePLA continuous fibers at a fiber draw speed from about 3000 in/min toabout 4000 in/min.

In accordance with certain embodiments, the calender comprises a pair ofcooperating rolls including a patterned roll. In such embodiments, thepatterned roll comprises a three-dimensional geometric bonding pattern.In some embodiments, the bonding pattern comprises at least one of adiamond pattern, a hexagonal dot pattern, an oval-elliptic pattern, arod-shaped pattern, or any combination thereof. In certain embodiments,the bonding pattern covers from about 5% to about 30% of the surfacearea of the patterned roll. In other embodiments, the bonding patterncovers from about 10% to about 25% of the surface area of the patternedroll. In some embodiments, the bonding pattern comprises the diamondpattern, and the bonding pattern covers about 25% of the surface area ofthe patterned roll. In further embodiments, the bonding patterncomprises the oval-elliptic pattern, and the bonding pattern coversabout 18% of the surface area of the patterned roll. In someembodiments, the calender comprises a release coating.

In accordance with certain embodiments, the nonwoven fabric comprisesbicomponent fibers. In some embodiments, the bicomponent fibers comprisea side-by-side arrangement. However, in other embodiments, thebicomponent fibers comprise a sheath and a core. In such embodiments,the sheath comprises PLA. In further embodiments, the core comprises atleast one of polypropylene, polyethylene, polyethylene terephthalate,PLA, or any combination thereof. In certain embodiments, the bicomponentfibers comprise PLA such that the sheath comprises a first PLA grade,the core comprises a second PLA grade, and the first PLA grade and thesecond PLA grade are different. In further embodiments, the sheathcomprises PLA, the core comprises at least one of polypropylene,polyethylene, or polyethylene terephthalate, and the system isconfigured to prepare the PLA continuous fibers at a fiber draw speedfrom about 3000 in/min to about 4000 in/min. In further embodiments,each of the sheath and the core comprises PLA, and the system isconfigured to prepare the PLA spunbond nonwoven fabric at a fiber drawspeed from about 3000 in/min to about 5500 in/min. However, in otherembodiments, the nonwoven fabric comprises PLA monocomponent fibers.According to certain embodiments, the PLA spunbond nonwoven fabriccomprises a spunbond fabric or a spunbond-meltblown-spunbond (SMS)fabric, wherein each of a spunbond web and a meltblown web comprisesfibers with PLA on a fiber surface.

In another aspect, certain embodiments according to the inventionprovide processes for preparing a PLA spunbond nonwoven fabric. Inaccordance with certain embodiments, the process includes providing astream of molten or semi-molten PLA resin, forming a plurality of PLAcontinuous filaments, depositing the plurality of PLA continuousfilaments onto a collection surface, exposing the plurality of PLAcontinuous filaments to ions, and bonding the plurality of PLAcontinuous filaments to form the PLA spunbond nonwoven fabric. Accordingto certain embodiments, forming the plurality of PLA continuousfilaments comprises spinning the plurality of PLA continuous filaments,drawing the plurality of PLA continuous filaments, and randomizing theplurality of PLA continuous filaments.

In accordance with certain embodiments, the process occurs at a fiberdraw speed greater than about 2500 in/min. In some embodiments, theprocess occurs at a fiber draw speed from about 3000 in/min to about5500 in/min. In further embodiments, the process occurs at a fiber drawspeed from about 3000 in/min to about 4000 in/min.

In accordance with certain embodiments, forming the plurality of PLAcontinuous filaments comprises forming bicomponent fibers. In someembodiments, forming bicomponent fibers comprises forming side-by-sidebicomponent fibers. In other embodiments, however, forming bicomponentfibers comprises forming bicomponent fibers having a sheath and a core.In such embodiments, the sheath comprises PLA. In further embodiments,the core comprises at least one of polypropylene, polyethylene,polyethylene terephthalate, PLA, or any combination thereof. In certainembodiments, the bicomponent fibers comprise PLA such that the sheathcomprises a first PLA grade, the core comprises a second PLA grade, andthe first PLA grade and the second PLA grade are different. In furtherembodiments, the sheath comprises PLA, the core comprises at least oneof polypropylene, polyethylene, or polyethylene terephthalate, and theprocess occurs at a fiber draw speed from about 3000 in/min to about4000 in/min. In some embodiments, each of the sheath and the coreconsist essentially of PLA, and the process occurs at a fiber draw speedfrom about 3000 in/min to about 5500 in/min. However, in otherembodiments, the nonwoven fabric comprises PLA monocomponent fibers.According to certain embodiments, the PLA spunbond nonwoven fabriccomprises a spunbond fabric or a spunbond-meltblown-spunbond (SMS)fabric, wherein each of a spunbond web and a meltblown web comprisesfibers with PLA on a fiber surface.

In accordance with certain embodiments, bonding the web to form the PLAspunbond nonwoven fabric comprises thermal point bonding the web withheat and pressure via a calender having a pair of cooperating rollsincluding a patterned roll. In such embodiments, thermal point bondingthe web comprises imparting a three-dimensional geometric bondingpattern onto the PLA spunbond nonwoven fabric. In some embodiments,imparting the bonding pattern onto the PLA spunbond nonwoven fabriccomprises imparting at least one of a diamond pattern, a hexagonal dotpattern, an oval-elliptic pattern, a rod-shaped pattern, or anycombination thereof. In certain embodiments, the bonding pattern coversfrom about 5% to about 30% of the surface area of the patterned roll. Inother embodiments, the bonding pattern covers from about 10% to about25% of the surface area of the patterned roll. In some embodiments, thebonding pattern comprises the diamond pattern, and the bonding patterncovers about 25% of the surface area of the patterned roll. In furtherembodiments, the bonding pattern comprises the oval-elliptic pattern,and the bonding pattern covers about 18% of the surface area of thepatterned roll. In some embodiments, the calender comprises a releasecoating.

In accordance with certain embodiments, the process further comprisesdissipating static charge from the PLA spunbond nonwoven fabricproximate to the calender via the static control unit. In someembodiments, the static control unit comprises a second ionizationsource. In further embodiments, the second ionization unit comprises anionization bar extending over at least one of the plurality of PLAcontinuous filaments or the PLA spunbond nonwoven fabric in a crossdirection. However, in other embodiments, dissipating static charge fromthe PLA spunbond nonwoven fabric comprises contacting the PLA spunbondnonwoven fabric with a static bar.

In accordance with certain embodiments, the process further comprisescutting the PLA spunbond nonwoven fabric to form cut PLA spunbondnonwoven fabric, exposing the cut PLA spunbond nonwoven fabric to ionsvia a third ionization source, and winding the cut PLA spunbond nonwovenfabric into rolls. In such embodiments, the third ionization unitcomprises an ionization bar extending over at least one of the pluralityof PLA continuous filaments or the PLA spunbond nonwoven fabric in across direction.

In accordance with certain embodiments, the process further comprisesincreasing humidity while forming the plurality of PLA continuousfilaments. In such embodiments, increasing humidity comprises applyingat least one of steam, fog, mist, or any combination thereof to theplurality of PLA continuous filaments.

Modifications of the invention set forth herein will come to mind to oneskilled in the art to which the invention pertains having the benefit ofthe teachings presented in the foregoing descriptions and the associateddrawings. Therefore, it is to be understood that the invention is not tobe limited to the specific embodiments disclosed and that modificationsand other embodiments are intended to be included within the scope ofthe appended claims. Although specific terms are employed herein, theyare used in a generic and descriptive sense only and not for purposes oflimitation.

That which is claimed:
 1. A process for preparing a polylactic acid(PLA) spunbond nonwoven fabric, the method comprising: providing astream of molten or semi-molten PLA resin; extruding the stream ofmolten or semi-molten PLA resin through a spin beam to form a pluralityof PLA continuous filaments; depositing the plurality of PLA continuousfilaments on a collection surface disposed below an outlet of the spinbeam to form the PLA spunbond nonwoven fabric; and exposing the PLAcontinuous filaments to ions from a first ionization source, wherein thefirst ionization source, and any additional ionization sources are allpositioned above the collection surface and downstream of a point atwhere the PLA continuous filaments are deposited on the collectionsurface.
 2. The process of claim 1, wherein the first ionization sourceis positioned prior to a first roll.
 3. The process of claim 2, whereinthe first roll is a press roll.
 4. The process of claim 1, furthercomprises a step of calendering the PLA spunbond nonwoven fabric.
 5. Theprocess of claim 4, wherein a calender is positioned downstream of thefirst ionization source.
 6. The process of claim 1, wherein the firstionization source and the collection surface are separated by a distancefrom about 1 inch to about 24 inches.
 7. The process of claim 5, furthercomprising a static control unit positioned and arranged to dissipatestatic from the PLA spunbond nonwoven fabric proximate to the calender,and wherein the static control unit comprises a passive static bar, or asecond ionization source.
 8. The process of claim 1, further comprisinga press roll positioned downstream from the outlet of the spin beam. 9.The process of claim 1, further comprising one or more of the following:a vacuum source disposed below the collection surface; a winderpositioned downstream from a calender; or a third ionization sourcepositioned and arranged to expose the PLA spunbond nonwoven fabric toions proximate to the winder.
 10. The process of claim 7, wherein atleast one of the first ionization source or second ionization sourcecomprises an ionization bar extending over at least one of the pluralityof PLA continuous filaments or the PLA spunbond nonwoven fabric in across direction.
 11. The process of claim 1, further comprising exposingthe PLA continuous filaments to ions from a second ionization sourcedisposed downstream of the first ionization source.
 12. The process ofclaim 11, further comprising exposing the PLA continuous filaments toions from a third ionization source disposed downstream of the secondionization source.
 13. The process of claim 12, where wherein the firstionization source, the second ionization source, and the thirdionization source are configured to actively dissipate static chargecreated during preparation of the PLA spunbond nonwoven fabric.
 14. Theprocess of claim 5, wherein a static control unit is positioned upstreamfrom, and adjacent to, the calender and/or positioned downstream from,and adjacent to, the calender.
 15. The process of claim 5, wherein thecalender comprises a pair of cooperating rolls including a patternedroll, the patterned roll comprising a three-dimensional geometricbonding pattern selected from the group consisting of one of a diamondpattern, a hexagonal dot pattern, an oval-elliptic pattern, a rod-shapedpattern, or any combination thereof.
 16. The process of claim 1, whereinthe PLA spunbond nonwoven fabric is drawn from the spin beam at a fiberdraw speed greater than about 2500 m/min.
 17. A process for preparing apolylactic acid (PLA) spunbond nonwoven fabric, the process comprising:providing a stream of molten or semi-molten PLA resin; forming aplurality of PLA continuous filaments in which PLA is present at asurface of the filaments; depositing the plurality of PLA continuousfilaments onto a collection surface; exposing the plurality of PLAcontinuous filaments to ions from a first ionization source, wherein thefirst ionization source, and any additional ionization sources are allpositioned above the collection surface and downstream of a point atwhere the PLA continuous filaments are deposited on the collectionsurface; and bonding the plurality of PLA continuous filaments to formthe PLA spunbond nonwoven fabric.
 18. The process of claim 17, whereinforming the plurality of PLA continuous filaments comprises: spinningthe plurality of PLA continuous filaments; drawing the plurality of PLAcontinuous filaments; and randomizing the plurality of PLA continuousfilaments.
 19. The process of claim 17, wherein forming the plurality ofPLA continuous filaments comprises forming bicomponent fibers, andwherein the bicomponent comprises side-by-side bicomponent fibers, orfibers having a sheath and a core.
 20. The process of claim 19, whereinthe sheath comprises PLA.
 21. The process of claim 19, wherein the corecomprises at least one of polypropylene, polyethylene, polyethyleneterephthalate, PLA, or any combination thereof.
 22. The process of claim19, wherein the bicomponent fibers comprise PLA such that the sheathcomprises a first PLA grade, the core comprises a second PLA grade, andthe first PLA grade and the second PLA grade are different.
 23. Theprocess of claim 19, wherein the process occurs at a fiber draw speedfrom about 3,000 in/min to about 5,500 in/min.
 24. The process of claim19, wherein the sheath comprises PLA, the core comprises at least one ofpolypropylene, polyethylene, or polyethylene terephthalate.
 25. Theprocess of claim 19, further comprising dissipating static charge fromthe PLA spunbond nonwoven fabric proximate to a calender via a staticcontrol unit.
 26. The process of claim 25, wherein the static controlunit comprises a second ionization unit.
 27. The process of claim 26,wherein the second ionization unit comprises an ionization bar extendingover at least one of the plurality of PLA continuous filaments or thePLA spunbond nonwoven fabric in a cross direction.